Embodiments of the disclosure relate to ultrasound imaging, and more particularly to shear wave elasticity imaging with improved shear wave velocity estimation.
Medical diagnostic ultrasound is an imaging modality that employs ultrasound waves to probe the acoustic properties of biological tissues and produce a corresponding image. Particularly, diagnostic ultrasound systems are used to visualize muscles, tendons, and many internal organs to capture their size, structure and any pathological lesions using near real-time tomographic images. Further, diagnostic ultrasound also finds use in therapeutic procedures where an ultrasound probe is used to guide interventional procedures such as biopsies.
Generation of ultrasound pulses and detection of the reflected energy is typically accomplished via a plurality of transducers located in the ultrasound probe in proximity or contact with a patient. Such transducers typically include electromechanical elements capable of converting electrical energy into mechanical energy for transmission and mechanical energy back into electrical signals on reception. These electrical signals are further processed and transformed into a digital image of the target region, such as biological tissues.
Recent ultrasound imaging techniques employ acoustically generated shear waves to determine the mechanical properties of biological tissues. Particularly, some of these techniques track shear wave induced displacements through a region of interest to determine tissue mechanical properties such as shear speed and shear elastic modulus. Shear waves are generated in a phantom or target tissues by delivering one or more pushing pulses to a target region. The pushing pulses typically have higher amplitudes and longer lengths than the acoustic pulses employed in B-mode or Color Doppler ultrasound imaging. Accordingly, the pushing pulses generate shear waves that travel from the point of generation through the tissue causing time varying displacements at multiple locations along the tissue. Further, the displacements caused by the shear wave may be detected using standard Doppler tracking pulses. Tracking the shear wave induced displacements as a function of time at the multiple locations allows an estimation of shear velocity, which in turn, is related to one or more mechanical properties of the tissue.
Characterization of tissue mechanical properties such as shear stiffness using shear velocity estimation has important medical applications as these properties are closely linked to tissue state with respect to pathology. Typically, at least a portion of a tissue may become stiffer than surrounding tissues indicating an onset or presence of a disease such as cancer, tumor, fibrosis, steatosis or other such conditions. Conventional shear velocity estimation techniques, however, suffer from inherently low signal-to-noise ratio (SNR) resulting in inefficient shear wave tracking, which may further result in erroneous velocity and stiffness computations. The erroneous stiffness values, in turn, may affect the accuracy of a medical diagnosis. Attempts to improve the SNR by increasing the amplitude and/or duration of the pulses used to create the shear waves may lead to increased acoustic radiation dosage for clinical use, and therefore may be unfeasible.
It is, thus, desirable to develop effective methods and systems for efficient shear wave elasticity imaging. Particularly, there is a need for methods and systems that, for example, improve the shear wave velocity estimation, frame rates and spatial resolution while optimizing the ultrasound radiation dosage.